1. Field of the Invention
The present invention relates to a cooking appliance such as a microwave oven, and more particularly, to a cooking appliance with an infrared sensor having a field of view within a heating chamber.
2. Description of the Background Art
Some of the conventional cooking appliances were provided with infrared sensors capable of detecting the temperature of food within heating chambers. In such a cooking appliance, the field of view of the infrared sensor was fixed to a position determined that the food was placed thereat, once the field of view started to move through the entire heating chamber simultaneously with the start of the heating. In the cooking appliance, the temperature of an object within the field of view was continuously or intermittently detected after the field of view was fixed, and the heating was stopped when the detected temperature reached the temperature at which the heating should be terminated.
It is noted that, in fixing of the field of view, the position assumed to have the food thereat was determined as follows. That is, the temperature is detected by moving the field of view to a plurality of points in the heating chamber, and a point at which the difference in the temperature between the point and the peripheral points is equal to or higher than a predetermined value is selected from the plurality of points. Thus, the selected point was determined as the position where the food exists.
However, in the conventional cooking appliance, when heating of a food item is carried out, for example, immediately after another food item was heated to a high temperature, even if the xe2x80x9cposition where food existsxe2x80x9d was incorrectly determined due to the partially raised temperature in the heating chamber, the heating operation would be continued in a state where the field of view was fixed at the incorrectly-determined position, i.e. where no food item exists in the field of view of the infrared sensor. Therefore, the cooking appliance could not surely grasp the temperature of the food item, which made it difficult to automatically control the progress of the heating of the food item.
The present invention was made in view of the foregoing, and it is an object of the present invention to provide a cooking appliance capable of including a food item placed in a heating chamber within a field of view of an infrared sensor.
A cooking appliance according to the present invention includes a heating unit heating an object to be heated; a heating chamber containing the object to be heated; an infrared sensor having a field of view within the heating chamber and detecting an amount of infrared radiation within the field of view; a field of view moving unit moving the field of view of the infrared sensor; and a temperature detecting unit detecting a temperature of an object within the field of view based on a detection output of the infrared sensor. The field of view moving unit is characterized by executing a first movement control moving the field of view by a predetermined pattern within the heating chamber simultaneously with or after a start of a heating operation of the heating unit; fixing the field of view at a predetermined position, which is a position having a temperature difference relative to a periphery equal to or higher than a predetermined value within the heating chamber, or a position having a largest temperature difference relative to the periphery within the heating chamber, in a detection temperature of the temperature detecting unit in the first movement control; and again executing a second movement control moving the field of view within the heating chamber based on satisfaction of a predetermined condition, after fixation of the field of view at the predetermined position.
Further, a method of controlling a cooking appliance according to an aspect of the present invention is made for a cooking appliance including a heating unit heating an object to be heated, a heating chamber containing the object to be heated, and an infrared sensor having a field of view within the heating chamber. The method of controlling includes the steps of executing a first movement control moving the field of view by a predetermined pattern in the heating chamber simultaneously with or after a start of a heating operation; detecting a temperature within the field of view, based on a detection output of the infrared sensor during a period in which the first movement control is being executed; determining a predetermined position, which is a position having a temperature difference relative to a periphery equal to or higher than a predetermined value within the heating chamber, or a position having a largest temperature difference relative to a periphery within the heating chamber, in a temperature within the field of view during the period in which the first movement control is being executed; fixing the field of view at the predetermined position; and executing a second movement control again moving the field of view within the heating chamber, based on satisfaction of a predetermined condition during a period in which the field of view is being fixed at the predetermined position.
According to the present invention, even if the field of view of the infrared sensor is once moved and fixed at the position determined to have the food item thereat as a result of the first moving control, the field of view can be moved again in the heating chamber if the predetermined condition is satisfied.
Therefore, the position of the field of view of the infrared sensor can be changed even after the field of view is once fixed at a position that was incorrectly determined to have the food item. This can more reliably avoid the situation in that the heating operation is continued in a state where no food item is included within the field of view of the infrared sensor.